The objective of this proposal is to explore the increase in the endogenous Ca2+-binding protein, calmodulin (CaM) and CaM-dependent functions that occur in rat brain after chronic treatment with the stimulant drug, amphetamine (AMPH). We found that treatment of rats with AMPH using a regimen that leads to behavioral sensitization (2.5 mg/kg/day x 5 d, withdraw 10 d) results in a 60% increase in the striatal content of CaM. In brain, CaM increases the activation of phosphodiesterase, protein kinase and adenylate cyclase, potentiates the activation of adenylate cyclase by dopamine and plays a role in synthesis and release of neurotransmitters. Recently it has been shown that CaM binds to a (3H) nitrendipine binding site in brain. The specific aims of this proposal are to: (1) examine the time course of development of the increase in CaM after withdrawal from AMPH in the rat striatum, limbic forebrain and frontal cortex and cerebellum and determine whether cocaine treatment elicits a similar increase in CaM; (2) determine the localization of the AMPH-induced increase in CaM using subcellular distribution and quantitative immunocytochemistry at the light and electron microscopic level. We will examine the localization of CaM-binding proteins using gel overlay and photoaffinity labelling; (3) examine selective CaM-stimulated activities (adenylate cyclase, cAMP phosphodiesterase, potentiation of dopamine-stimulated activity and phosphorylation of synapsin I and (3H) Nitrendipine binding) after AMPH treatment. Female rats will be used since they demonstrate greater behavioral sensitization to AMPH than male rats. Thus we will investigate the characteristics and localization #f the increase in CaM after AMPH treatment and determine which activities are altered as a consequences of this increase. The finding of a significant increase in CaM suggests a high demand for a Ca2+ and CaM-stimulated process in a certain pathophysiological state. Study of the localization and CaM-mediated activation of certain enzymatic processes should increase our understanding of neurochemical and behavioral events that occur as a result of chronic treatment with stimulant drugs.